Basically a medicament delivery device is a device that is simple to use without the need of performing many steps when an individual has to administer a dose of medicament by himself/herself. This requires a solution able of keeping a medicament delivery device as pre-assembled and ready as possible, in order to deliver the medicament in a measured dosage, without many manual operations or actions. Thus, to minimize the number of steps needed, in order to perform a medicament delivery, some known prior art devices only need to be actuated against the delivery area, without the need of manual actuation, by pressing a button or the like, which causes the medicament delivery device to perform the delivery. There is however a common request for a medicament delivery device which is very easy to use and which can reliably deliver a set dose of a medicament in a safe way.
U.S. Pat. No. 5,925,021 discloses a pen injector device comprising a locking means for locking the actuator knob in a depressed position, a start button for releasing the actuator button and a dosage knob for setting a prescribed dose. U.S. Pat. No. 5,925,021 also comprises electronics, such as sensors and display devices for controlling the injection, for measuring and storing ejected doses and for displaying information to the user. A disadvantage of this prior art is that a dose needs to be set and then injected manually by pushing the actuator button until it stops. In a stressful situation, or if handled by an inexperienced user, the injection may be interrupted mid-way and the button may be released inadvertently. If the button is depressed again, i.e. without adjusting the dosage, a new dose of the previous setting will be initialized, which will lead to the patient receiving an overdose.
There is therefore a need for an arrangement that can provide safe and simple handling both by inexperienced users and in stressful situations. Hence, there is a need for an arrangement where a predetermined dosage is fully delivered, i.e. an arrangement for administering a predetermined dose such that the delivery of a previously initialized dose of medicament has to be fully completed before delivery a subsequent predetermined dose can be initialized. Thus, as can be noted, human handling aspects of the medicament delivery device are crucial and there are several rationales for improving existing solutions.